The prior art relating to internal combustion engines contains numerous examples of plenum type ram tube intake manifolds designed to provide optimum breathing characteristics for supplying intake air charges to the cylinders of internal combustion engines. Such manifold arrangements have been applied primarily to engines having port or cylinder fuel injection and spark or compression ignition where the fuel charge is not required to pass through manifold runners, or ram tubes, of extensive length in order that deleterious effects upon fuel delivery and distribution may be avoided.
While the specific designs of intake manifolds may vary for differing engine applications, the common elements of ram tube plenum type manifolds include one or more intake plenums or air chambers into which intake air is received and from which individual intake runners, or ram tubes, extend to the intake ports of the engine cylinders. The size of the plenum or plenums and the length and cross-sectional area of the ram tubes are selected in accordance with recognized resonator concepts, supplemented by performance testing, to provide resonant tuning of the intake charges that accentuates specific desired breathing characteristics to obtain desired or optimum performance of the specific engine involved. The location and configuration of elements of the manifold structure may be varied to suit the circumstances of the engine and engine compartment design, including the size and location of available space. It is noted however that most such prior art manifold designs have required considerable space in the engine compartment for their application to automotive engines.